Light beams or optical signals are frequently used to transmit digital data, for example, in fiber optic systems for long-distance telephony and internet communication. Additionally, much research has been done regarding the use of optical signals to transmit data between electronic components on circuit boards.
Consequently, optical technology plays a significant role in modern telecommunications and data communication. Examples of optical components used in such systems include optical or light sources such as light emitting diodes and lasers, waveguides, fiber optics, lenses and other optics, photo-detectors and other optical sensors, optically-sensitive semiconductors, optical modulators, and others.
Systems making use of optical components often rely upon the precise manipulation of optical energy, such as a beam of light, to accomplish a desired task. This is especially true in systems utilizing light for high-speed, low-energy communication between two nodes. Often optical resonators are used to selectively filter, switch, or modulate light beams.
When light of the appropriate wavelength is introduced into the resonator, the light beam builds up in intensity due to constructive interference. Alternatively, light of a wavelength apart from the resonant frequency or range of the resonator is attenuated by destructive interference.
Optical resonators are often used to modulate data onto optical beams by varying the resonant frequency. This can be done by altering an effective index of refraction of the resonator, therefore causing a shift in the resonant frequency of the ring resonator. The index of refraction can be shifted by altering a free carrier concentration within the resonator (i.e. selectively injecting or removing charge carriers) or by altering the temperature of the resonator. Often it is desirable to maintain the resonator at a constant temperature while modulating the data onto the optical beam by selectively injecting and removing charge carriers. The temperature at which the resonator is maintained may be determined by a base resonant frequency at which it is desired that the resonator operate.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.